More than 300 bicyclists were arrested during the demonstrations against the Republican National Convention. While the riders were released within days, many of their bikes have been locked up for three weeks.

Yesterday, the Manhattan district attorney's office agreed to let protesters retrieve them from the property clerk in Greenpoint, Brooklyn.

The deal was worked out by Norman Siegel, a civil rights lawyer representing the bicyclists. ''I'm pleased the D.A.'s office has arranged to have the bikes released,'' he said. ''To have kept the bikes would've been punitive and legally unnecessary.''

The matter of the seized bicycles has been a little-noticed footnote to the ongoing legal disputes over mass arrests during the demonstrations, with complaints that innocent people were swept up in them and many were detained for long periods in violation of court orders.

The police said yesterday that 354 bicycles were seized during convention protests and that they had been held as evidence pending the disposition of cases. Mr. Siegel said that he and the prosecutors had agreed that instead of holding onto the bicycles until trials, which could be at the end of this year or the beginning of 2005, the bicycles would be photographed and released.

Barbara Thompson, a spokeswoman for the office of the district attorney, Robert M. Morgenthau, said that some bicycles were returned yesterday under the new agreement.

''After review, we decided that photographs would suffice and the bicycles could be returned,'' she said.

To retrieve a bicycle, the owner must present the property voucher, given at the time of arrest, at the district attorney's office and obtain a release form to show to the property clerk in Brooklyn. Bicycles played a significant role during the Republicans' visit. On Aug. 27, the Friday before the convention, about 5,000 bicyclists shouting ''No more Bush!'' hurtled past Madison Square Garden. Later that night, more than 250 of them were arrested after a protest ride that ended in the East Village. Many of the arrests were made outside St. Mark's-in-the-Bowery Church on Second Avenue, and most were on charges of disorderly conduct or obstructing traffic. Many bicyclists said they were arrested even though they had broken no traffic laws.

For those who rely on bicycles for transportation, being deprived of them has been a hardship. Randall Steketee, 26, a paralegal for a law firm in the financial district, said he was riding home to the East Village from work that Friday when he found himself near a group of bicyclists at the end of the protest. Mr. Steketee said that he was mistakenly arrested on Second Avenue, and that the police seized his brand-new Cannondale hybrid.

''I ride my bike to work every day, and I use it to get around town'' he said. ''Now every time I want to go somewhere, my commute is almost doubled.''

Shortly after the convention, Time's Up!, an environmental advocacy group that promotes the use of bicycles and that had participated in the protest, began holding meetings in an East Houston Street storefront to discuss the seizures. Several bicycles that were seized belonged to the group and had been lent to people during the convention.

Some bicyclists said they thought that the original decision to hold onto the bikes had penalized those who insisted on going to trial. But Ms. Thompson said that a handful of bicycles had been returned to people who had been arraigned and were waiting for a trial.

Other bicyclists said that their bicycles had been taken by the police while legally locked up on the sidewalk. Police officials said they had no indication that any locks were cut.

''Our goal is for this not to happen again,'' said Bill DiPaola, the executive director of Time's Up!